The invention relates to a magnetic release for a switching device in particular for a circuit breaker. The magnetic release has a coil, a core located inside the coil and an armature that may be in the form of a plunger-type armature moving inside the coil or in the form of a hinged armature.
A magnetic release, in particular for a circuit breaker, contains a coil which is produced from wire wound in a helical shape, a magnet core which is firmly connected to a yoke surrounding the coil on the outside and which engages in the interior of the coil, and a magnet armature which is either in the form of a hinged armature or a plunger-type armature, with the latter likewise being located inside the coil. In one known configuration, the core and the armature are located inside a cylindrical tube, with the armature being held at a distance from the core by a compression spring, so that the armature is attracted towards the core, against the force of the spring, when an overcurrent or short-circuit current is present. At one end, the coil is connected to the yoke, which at that point has a holder for a thermal bimetallic strip and at the other end is fitted with a stationary contact piece, which merges into an arc guide rail which bounds an arc splitter stack on the release side and feeds the base of the arc which is produced on the stationary contact piece to the arc splitter stack.
In a configuration such as this, an insulated wire composed of copper must be stripped and wound into a helical shape at the ends in order to produce the coil, which involves the use of a large amount of labor time. Furthermore, the coil must also have an associated yoke, to which the coil tube is fitted, and around which the insulated wire is wound and is guided in the armature and core. Production of this configuration is costly.
It is accordingly an object of the invention to provide a magnetic release, in particular for a circuit breaker, and a circuit breaker having such a magnetic release that overcomes the above-mentioned disadvantages of the prior art devices of this general type, whose manufacture is simplified.
With the foregoing and other objects in view there is provided, in accordance with the invention, a magnetic release for an electrical switching device. The magnetic release contains a coil being stamped and bent from sheet metal composed of a material being electrically highly conductive and magnetically highly permeable. The coil has first webs disposed at a given distance from one another in a first plane and second webs disposed at the given distance from one another in a second plane and in each case run parallel to one another and offset with respect to one another. The coil has connecting webs in each case disposed between one end of one of the first webs and an adjacent end of one of the second webs and in each case one end of one of the second webs and an adjacent end of one of the first webs. The first webs, the second webs and the connecting webs are disposed in such a manner that the first webs, the second webs and the connecting webs are in a helical shape around a center axis. The first webs, the second webs and the connecting webs define an inside region in a form of a through-opening, the coil additionally having a stationary contact piece of a contact point for a circuit breaker. A holder for a thermal release is integrally formed on the coil and a core is accommodated in the through opening of the coil. An armature of a plunger-type armature moving inside the coil or a hinged armature is provided.
According to a further refinement of the invention, an arc guide rail for an arc splitter stack is then integrally formed on the stationary contact piece. An arc splitter stack, for quenching, is integrally formed on the arc guide rail, inside the electrical switching device.
In addition, a core can also be integrally formed on the coil. More specifically, an L-shaped lug can be integrally formed at one end on the coil, the L-shaped lug having a free limb projecting into a coil area on its center axis, and forms the core.
The coil, the stationary contact piece, the arc guide rail and the holder for the thermal release, possibly together with the core, thus form a unit. There is no longer any need for wire windings. Since the coil is formed from sheet iron, there is likewise no longer any need for an autonomous yoke.
A coil as such, without a stationary contact piece, arc guide rail and holder for the thermal release, has been disclosed per se in German Patent DE 6 66 920. The coil is essentially used as a field coil for synchronized machines or direct-current machines, to be precise in order to replace the flat conductors, wound on edge.
Such a refinement of the coil can be produced easily by stamping from a metal sheet and by folding and bending, so that there is no longer any need for special winding apparatuses with a winding mandrill or the like.
According to a further embodiment, the first and second webs are U-shaped, with the U-shape of the first and second webs each being open towards the opposite plane.
The connecting webs can then advantageously be connected alternately at one end of each web to one limb of the U-shape and at the other end to the other limb of the U-shape.
This results in a concertina-like coil which is stamped and bent in a helical shape from sheet metal composed of a material which is electrically highly conductive and magnetically highly permeable, in which case there is no need to coat the sheet metal with an insulating material, since the individual turns do not touch one another.
In accordance with an added feature of the invention, the connecting webs each assume an angle to one another, and one of the connecting webs runs parallel to another, over others of the connecting webs. The connecting webs can also run parallel to one another at right angles to the center axis.
A circuit breaker can be formed of the magnetic release as described above. The circuit breaker has a housing with inner surfaces, mutually opposite ones of the inner surfaces have strips that engage between coil turns in order to guide the coil.
In accordance with a further feature of the invention, the strips are configured such that they are used to guide the core and/or the armature.
In accordance with a concomitant feature of the invention, an arc guide rail is integrally formed on the coil. The core, the stationary contact piece and the arc guide rail are disposed at one end of the coil, and the holder for the thermal release is disposed at another end of the coil.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a magnetic release, in particular for a circuit breaker, and a circuit breaker having such a magnetic release, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.